The field of art to which this invention pertains is structural acrylic adhesives.
Structural acrylic adhesives are rubber-toughened adhesive systems that cure rapidly at room temperature to give excellent adhesive properties. Such adhesives are characterized by high peel strength, shear strength and chemical resistance. They are also tolerant of a variety of substrate surface contaminants, such as oil.
Fast curing adhesives are described in U.S. Pat. No. 3,832,274. These adhesives are made from elastomers having Tg of less than 15.degree. F., acrylic monomers and a redox catalyst.
Structural adhesives which contain chlorosulfonated polyethylene or sulfonyl chloride and chlorinated polymers are disclosed in such patents as U.S. Pat. Nos. 3,890,407, 3,962,372 and 4,287,106.
U.S. Pat. Nos. 4,126,504, 4,348,503 and 4,451,615 disclose various combinations of elastomers, acrylic monomers, catalysts and other additives.
Adhesives based on diene polymers, such as polybutadienes, polyisoprenes, butadiene-styrene copolymers and ABS graft polymers, plus vinyl monomers, adhesion promoters and the like are described in U.S. Pat. No. 4,287,106.
Methacrylate based adhesives which contain chlorinated or chlorosulfonated polyethylene polymers and graft copolymers of the core-shell type are disclosed in U.S. Pat. No. 4,536,546.
With the use of more and more plastics in structures, e.g., automobiles, there is a continuing and even increasing need for adhesives which can be used on plastics as well as metals to form bonds which will hold up under a wide variety of adverse conditions.
There is a particular need for structural adhesives which not only have high adhesive bond impact strength but also have high bulk tensile elongation when measured at low temperatures.